Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades are the primary elements for converting wind energy into electrical energy. The blades typically have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between its sides. Consequently, a lift force, which is directed from the pressure side towards the suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is geared to a generator for producing electricity.
Typically, a wind turbine is designed to operate at its rated power output over a predetermined or anticipated operating life. In many instances, this anticipated operating life is limited by or based upon the anticipated component life of one or more of the wind turbine components (referred to herein as “life-limiting components”). For instance, FIG. 1 illustrates example data for a conventional wind turbine having an anticipated operating life 100 (ending at dashed line 102) that is defined by the anticipated component life (indicated by component life curve 104) of one or more of its life-limiting components. As shown in FIG. 1, as the wind turbine is operated at its rated power over time (indicated by constant rating curve 106), the remaining component life for its life-limiting component(s) decreases linearly along the component life curve 104 from 100% at the wind turbine's initial start-up to about 50% at the midpoint of the turbine's anticipated life (indicated by point 108) and then to about 0% at the end 102 of the turbine's anticipated operating life 100. Thus, for such a wind turbine (assuming no other limiting or constraining design factors), the anticipated operating life 100 for the turbine is defined by the anticipated operating life of such life-limiting component(s).
Additionally, for many wind turbines, the rated power output associated with each wind turbine is well below the instantaneous maximum power output that may be achieved. Thus, it is often desirable to uprate a wind turbine in order to maximize its total power output. However, such uprating results in increased loading on the wind turbine components, thereby reducing component lives. As such, for a wind turbine having an anticipated operating life that is limited based on the anticipated component life of one or more life-limiting components, uprating the wind turbine can significantly reduce its overall operating life.
Accordingly, a system and method for controlling a wind turbine that allows the turbine's power output to be increased over an early portion of its operating life in order to increase the turbine's net present value without resulting in a reduction in the overall operating life of the turbine would be welcomed in the technology.